There have been conventionally known image printing apparatuses each of which ejects ink from a plurality of nozzles provided in a print head and prints an image on a printing medium conveyed by a conveyance device. Such image printing apparatuses include an apparatus of a single-pass system which is provided with a plurality of print heads, covers the entire printing width in a width direction orthogonal to a predetermined conveyance direction of a printing medium conveyed in the conveyance direction with the entire row of nozzles included in the plurality of print heads, and thus performs image formation without causing the print heads to scan in the width direction.
In an image printing apparatus configured in such a way, a positional shift from an appropriate position of a print head is detected by printing a line pattern including a line printed by ink ejection from an individual nozzle of each of the print heads on a printing medium and reading the position in the width direction of the line pattern with a line sensor provided downstream in the conveyance direction (for example, Patent Document 1).